1. Field of the Invention
The present invention relates to a method for determining the optimal order in which a mounter is to mount electronic components onto a board, such as a printed circuit board. In particular, the invention relates to the optimization of the order of component mounting for a mounter equipped with a line gang pickup head that picks up a plurality of components and mounts them onto the board.
2. Background of the Related Art
The order in which a mounter mounts electronic components on a board such as a printed circuit board is conventionally optimized to minimize a tact time (i.e., the time taken by mounting). Recently, with diversification of the types of electronic devices, there has been an increase in demand for a multi-functional mounter equipped with a line gang pickup head based on a method referred to as “gang pickup” of picking up a plurality of components and mounting them on a board. Thus, various types of methods for optimization of the order of component mounting for such a mounter are presented (for instance, in Japanese Laid-Open Patent Applications No. 2002-50900 and No. 2002-171097).
The reference mentioned above discloses the method for optimizing an order of component mounting in favor of the mounting of the components performed by a line gang pickup head, namely, prioritizing the maximization of the number of components to be simultaneously picked up by a line gang pickup head per task. Here, one iteration of repeated series of processes where a line gang pickup head picks up, transfers and mounts components, and the group of components handled in such an iteration are both referred to as a “task”. The number of tasks required for mounting all the components is minimized owing to such optimization, and therefore, the mounting of the components can be completed with a shorter tact time.
However, the above conventional optimization method takes a lot of processing time to simultaneously determine various conditions for optimization, such as: a Z-axis arrangement which is an array of component feeders to be set on a mounter; an arrangement of nozzles at a nozzle station; a nozzle pattern; and a mounting order (i.e., an order of mounting components in consideration of mounting points on a board). To be more specific, it is a method for searching the conditions optimal on the whole by checking the tact as well as various constraints each time the above conditions for optimization are changed. Therefore, it is necessary to calculate a tact each time the nozzle pattern is changed and thereby it takes time for optimization. Here, a nozzle pattern is a pickup nozzle string in which a type of nozzle for picking up components is determined for each line gang pickup head in each task that is arranged according to the mounting order.
It is also a problem that an optimal solution cannot always be found since a head position and a task and others of the line gang pickup head to be interchanged are determined using random numbers in order to change the conditions for optimization.